Methods for the detection of harmful substances or traces thereof

ABSTRACT

The presence of carcinogens in air, soils, and other areas is detected by combining liquid-assisted air sampling with means for testing liquid samples for mutagenicity. Hazardous or illicit substances or pathogens which may be buried in the ground or otherwise concealed or present in contaminated food at various stages of food processing are detected using a two-line probe such that one of the lines directs exhaust air from the sampler onto suspect surfaces so as to dislodge and blow off droplets, particles or insects therefrom while the other line draws some of them into the sampler. Variants of said two-line probe can also serve to collect lead, hexavalent chromium or other harmful substances and bacterial, fungal or viral pathogens from crumbling walls or floors. Liquid-assisted air sampling can also serve to capture disease-transmitting insects and detect and identify insect-borne pathogens.

REFERENCE TO RELATED APPLICATIONS

This is a continuation in part of application Ser. No. 08/377,966, filedJan. 25, 1995, now abandoned and of application Ser. No. 08/851,428,filed May 5, 1997 now U.S. Pat. No. 6,087,183. Application Ser. No.08/377,966 is a continuation of application Ser. No. 07/931,572, filedAug. 10, 1992, now abandoned, and a continuation-in-part of applicationSer. No. 08/255,712, filed Jun. 7,1994, now abandoned, which wascontinuation-in-part of application Ser. No. 07/993,080, filed Dec. 18,1992 now U.S. Pat. No. 5,328,851. Application Ser. No. 08/851,428 filedMay 15, 1997, now U.S. Pat. No 6,087,183, is a continuation-in-part ofapplication Ser. No. 08/255,712, filed Jun. 7, 1994, now abandoned,which was a continuation-in-part of application Ser. No. 07/931,572,filed Aug. 10, 1992, now abandoned and of application Ser. No.07/993,080, now U.S. Pat. No. 5,328,851.

U.S. Pat. No. 5,328,851 was a divisional application of application Ser.No. 07/499,602, filed Mar. 26, 1990, now U.S. Pat. No. 5,173,264, whichwas a continuation-in-part of U.S. applications Ser. No. 07/330,654,filed Mar. 30, 1989, now U.S. Pat. No. 4,912,051, and Ser. No.07/330,655, filed Mar. 30, 1989, now U.S. Pat. No. 4,977,095

The disclosures of all of said applications and patents are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

This invention relates to improved apparatus and methods for detectingharmful substances, whether airborne or grounded, whether biological orchemical, which may pose an immediate or long term hazard to human lifeor health.

In my afore-cited co-pending applications, I have disclosed apparatusand methods for collecting various contaminants—including vapors andparticles, chemical or biological—from a large volume of air into asmall volume of carrier liquid, so as to permit or facilitate rapid andultra-sensitive detection of traces of hazardous or illicit substanceswhich may be otherwise difficult to detect. The collected contaminantsmay be either dissolved by or suspended in the carrier liquid.

My earliest apparatus was intended mainly for the absorption of vaporsby the carrier liquid and was therefore referred to as liquid-absorptionair sampler. With subsequent use of the same apparatus for thecollection of respirable particles, the term “absorption” becameinappropriate, as the collected particles remain suspended in thecarrier liquid without being dissolved therein. Such apparatus andmethods will therefore be referred to herein as “HTLAAS” forHigh-Throughput Liquid-Assisted Air Sampling, which applies to collectedair contaminants which are either dissolved or suspended in a carrierliquid.

The present disclosures deal with several improvements and new potentialapplications of said apparatus and methods which extend theapplicability of the HTLAAS technology to new uses and to previouslyunmanageable or borderline atmospheric conditions. Some of the new usesinclude collection of pathogen-bearing insects. For the sake of brevity,collected insects will also be referred to as “particulates,” especiallyafter being killed or incapacitated in a HTLAAS device.

The applicability of HTLAAS devices can be extended to various types ofhazards which have been heretofore dealt with by other means in muchless cost-effective ways. For instance, the present approach of theEnvironmental Protection Administration [EPA] is to monitor air, soils,and other areas for the presence of certain listed known or potentialcarcinogens, while possibly overlooking some unlisted ones. Therefore asingle generalized method of monitoring for mutagenicity will not onlybe much more cost-effective than monitoring for a multiplicity of listedcarcinogens but will also alert people to the presence of possiblecarcinogens which are not included in EPA's list. In a recentwell-publicized case, an increased incidence of brain tumors amongworkers in an Amoco laboratory could not be connected to the use orpresence of any known carcinogen using existing analytical methods. Theuse of a water-assisted air sampler in conjunction with any of the knownmethods of testing aqueous solutions for mutagenicity, as claimed in myafore-listed co-pending applications, may thus provide a far morecost-effective and more powerful carcinogen alert than what is beingused at present.

It is therefore another object of this invention to provide acost-effective method and instrumentation for monitoring ambient air,soils, and other areas for mutagenicity.

A good measure of the performance of HTLAAS devices is the concentrationfactor F, which is proportional to the ratio of the concentrations inthe liquid carrier and in air of the monitored air contaminant,hereinafter referred to as “analyte.” The concentration factor F isdefined by the equation

F=εS/v _(L)  [1],

where ε is the sampler's collection efficiency, S is its air samplingrate, and v_(L) is the volume of liquid in which the analyte iscollected.

Most of the previous work on concentrating airborne contaminants into acarrier liquid sought to maximize the collection efficiency and the airsampling rate within the limits imposed by size, weight, and powerrequirements. No serious attention was given to increasing theconcentration factor F by minimizing v_(L). Yet by gathering thecollected contaminants into a ten-fold smaller liquid volume we canachieve a 10-fold increase in their concentration within the liquid andhence in the overall sensitivity of the system.

It is therefore an object of this invention to greatly enhance thedetection sensitivity of systems using liquid-assisted collection ofairborne contaminants by minimizing the volume of the liquid into whichsaid contaminants are gathered.

Present collection systems utilize primarily water-based carrierliquids, which have two important shortcomings, namely: [1] loss ofwater by evaporation during the sampling process; and [2] freeze-up ofwater at temperatures near or below 0 C. It is therefore also an objectof this invention to overcome these shortcomings by substituting for thewater an alternative carrier liquid having a much higher boiling pointand lower freezing point.

Presently known water-assisted air-sampling systems have been usedsolely for detecting the presence of various of chemical or biologicalcontaminants in ambient air. However, the same systems may also offerimportant advantages in the detection of concealed explosives, illicitdrugs, or contaminated foods. It is therefore yet another object of myinvention to provide an adapter that will permit collection by aliquid-assisted air sampling system of vapors or particles deriving fromconcealed hazards or illegal activities.

It is also an object of my invention to provide improved cost-effectiveapparatus and methods for capturing mosquitoes and otherdisease-transmitting insects in sufficient numbers to permit detectionand identification of insect-borne pathogens.

Other objects of my invention are to provide an electronicallyprogrammable interface between a collector and a detector, so as toyield an automated or quasi-automated collection-detection system, toreduce the size and weight of the overall system, and to further enhancethe system's sensitivity by further increasing its collection efficiencyand air sampling rate.

More objects of the invention will become apparent to professionals inthe chemical and biological defense, law enforcement, health monitoring,disease control, industrial safety and hygiene, environmental, chemical,metallurgical, and related areas following perusal of the completespecification.

SUMMARY OF THE INVENTION

Briefly, the invention consists of extending the applicability ofliquid-assisted air samplers to several new uses and to operation ofsuch samplers under extreme climatic conditions. The new uses areeffectuated in the following ways:

1. Providing generalized means and methods of detecting the presence ofcarcinogens in air, soils, and other areas by combining liquid-assistedair sampling with means for testing liquid samples for mutagenicity.

2. Providing means and methods of detecting the presence of hazardous orillicit substances or pathogens which may be buried in the ground orotherwise concealed or present in contaminated food at various stages offood processing, said means comprising a two-line probe such that one ofthe lines directs exhaust air from the sampler onto suspect surfaces soas to dislodge and blow off droplets, particles or insects therefromwhile the other line draws some of them into the sampler. Variants ofsaid two-line probe can also serve to collect lead, hexavalent chromiumor other harmful substances and bacterial, fungal or viral pathogensfrom crumbling walls or floors.

3. Providing means and methods of capturing disease-transmitting insectsand detecting and identifying insect-borne pathogens.

4. Extending the sampler's operational range to extreme climaticconditions by substituting an organic low-vapor-pressurelow-freezing-point carrier liquid, such as mineral oil, corn oil, ordimethyl sulfoxide, for the water in present liquid-assisted airsamplers.

5. Extending the range of detectability of sampler-detector systems tolower air concentrations and smaller particle sizes by minimizing v_(L)and increasing S and ε of Equation 1. The minimization of v_(L) isachieved by transferring the collected analyte from an organic carrierliquid into a tiny volume of water, taking advantage of the differencesin the densities of these liquids. The increases in S and ε are achievedby further improvements in sampler design.

6. The afore-said minimization of v_(L) is preferably accomplished aspart of an electronically programmable collector-detector interfacewhich is geared for automated or quasi-automated air monitoring.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best explained with reference to the drawings, inwhich:

FIG. 1 is a block diagram of the air and liquids flow system in severalpreferred embodiments of my invention;

FIG. 2 is a cross-sectional view of one variant of the device 5 of FIG.1 together with a novel attachment thereto;

FIG. 3 shows two sectional views of one of several sampling tubules inanother variant of device 5;

FIG. 4 is a cross-sectional view of an improved expansion chamber 7 inthe device 5 of FIG. 1; and

FIG. 5 is a schematic diagram of a novel concentrating device in anotherpreferred embodiment of my invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The block diagram of FIG. 1 outlines the air and liquids flows inseveral preferred embodiments of my invention. Starting at the airintake line 1, the sampled air is drawn through an electricallyprogrammable intake control valve 3 into a HTLAAS device 5, such as isdescribed in my co-pending application Ser. No. 08/851,428, filed May 5,1997, or in conjunction with my below-discussed FIGS. 2 and 3. Afterbeing partly scrubbed of its contaminants, the air is exhausted througha flow expansion chamber 7 by an air blower 9 into an air exhaust line11. The design of expansion chamber 7 is shown in the below-explainedFIG. 4.

The liquids flow circuits include the HTLAAS 5, the concentrator 25,liquid reservoirs 13, 13′ . . . , and micro-pumps 15, 15′ . . . forfeeding metered doses of mineral oil and aqueous medium to the HTLAASand concentrator, respectively, a programmable valving controlcomprising a multi-channel solenoid valve 17, and interconnecting lines16, 16′ . . . , 21, 23, 27, and 29, which are shown in the left andlower portions of FIG. 1 as double lines to distinguish them from theair flow circuit [drawn as single lines]. The electrically programmablevalving control or multi-channel solenoid valving system 17 is used toclose or open any of the lines 16, 16′ . . . , 19, 21, 23, and 27 ofFIG. 1 at predetermined intervals.

The liquids flow system comprises liquid reservoirs 13, 13′ . . . ,electronically controllable micro-pumps 15, 15′ . . . , a programmablemulti-channel solenoid valve 17, and connecting lines 16, 16′ . . . ,19, 21, 23, 27, and 29. One or more liquid reservoirs 13, 13′ . . .supply one or more liquids to a conical cavity 14 of the HTLAAS device 5via micro-pumps 15, 15′ . . . , liquid supply lines 16, 16′ . . . ,electrically programmable valving 17, and a liquid feed line 19. Theliquid that is contained in the conical cavity 14, which serves as aliquid input chamber, is impacted by part of the air stream that isdrawn in through the intake line 1, whereby droplets are formed andcarried over so as to deposit as a swirling liquid film on the innerwall of a sampling tube 105 [FIG. 2], as described in my afore-citedco-pending application Ser. No. 08/851,428. At high air flow rates, someof that liquid is carried over and accumulates in the expansion chamber7, whence it is either recirculated into the conical cavity 14 via line21, valving 17, and feed line 19 or is diverted by valving 17 and line23 into a concentrator 25.

Also fed into concentrator 25 is a scavenging liquid from one of thereservoirs 13, 13′ . . . , micro-pumps 15, 15′ . . . , and supply lines16, 16′ . . . through valving 17 and a scavenger supply line 27. Theresulting contaminant-enriched scavenging liquid is fed fromconcentrator 25 to a detector 31 via a concentrated sample line 29,while the excess of depleted liquid is discarded via a waste line 33.

At appropriately programmed times, one or more liquid reservoirs supplya selected liquid to the HTLAAS via its associated micro-pump, thesolenoid valve 17, and line 19; another reservoir supplies a scavengingsolution 76 [FIG. 5] to a concentrator 25 via its micro-pump and line27; and contaminant-enriched liquid carrier is fed by gravity from theexpansion chamber 7 through line 21, valve 17, and line 23 into theconcentrator 25 at time intervals and for durations controlled by theprogramed solenoid valve. The liquids flow system of FIG. 1 permitsautomated feeding of particulate-enriched liquid samples to detector 31,which may comprise any appropriate sensor or array of sensors.

The device 5 of FIG. 1 may be any suitable high-throughput sampler inwhich a substantial part of contaminants from the sampled air isretained within a liquid solution or suspension. The portable HTLAAS ofmy co-pending application Ser. No. 08/851,428 and the apparatusesdisclosed in my other above-referenced applications and patents areincluded in this category. Also included are modified versions of thesedevices, such as those indicated in FIGS. 2 and 3.

FIG. 2 shows a Portable HTLAAS or PHTLAAS 60, such as that shown in FIG.5 of my co-pending application Ser. No. 08/851,428 and described indetail therein. An adapter 301 to the air inlet 102, similar to thatshown in FIG. 17 of said co-pending application, is connected to the airintake line 1 by a smoothly curved arm 305 of an inverted Y-junction. Asecond, straight, arm of the Y-junction serves as a large particles trap315, ending with a capped opening 318 which provides access for removalof the trapped large particles at appropriate time intervals. As air isdrawn through arm 305, the suspended smaller particles follow the curvedstreamlines, whereas the inertia of the larger particles causes them tocontinue along a straight path into trap 315. Any accumulation of largeparticles can be removed from trap 315 by uncapping the opening 318.Such a Y-junction serves to intercept interfering large particles [>10microns in size] in cases where only respirable [<10-micron-size]particles are to be monitored.

As shown in FIG. 2, the PHTLAAS 60 comprises an outer protective tube106 and an inner sampling tube 105 leading to the expansion chamber 7.However, to improve the collection efficiency for smaller particles [1-2microns or less in size], without significantly increasing the requiredpower consumption, it may be advantageous to replace the single tube 105by several smaller sampling tubules, such as that shown in FIG. 3.

The rationale for replacing the single sampling tube of the PHTLAAS by aplurality of smaller tubules is that the minimum particle size that canbe collected by a cyclone or similar air sampler is proportional to thesquare root of its diameter [see, e.g., J. H. Maas, “Gas-SolidSeparations,” in Handbook of Separation Techniques for ChemicalEngineers, P. A. Schweitzer, editor-in-chief, Section 6.1, pp. 6-3through 6-17, McGraw-Hill, N.Y. 1979]. This implies that a four-foldreduction in sampling tube diameter should raise the collectionefficiency for 1-micron particles to the value that is obtainable with2-micron particles and the larger diameter.

It also follows from the equations governing the design and performanceof cyclone collectors that multiple tubules of smaller diameter yieldhigher collection efficiencies than a single large tube under otherwisecomparable conditions, even if the tubules are of shorter length thanthe large tube. With shorter tubules, the required power decreases forotherwise comparable flows.

For instance, in the PHTLAAS of FIG. 2, the single 1.1″ sampling tube105 was replaced by three parallel 0.53″-I.D. sampling tubules, such astubule 68 of FIG. 3. To induce a swirling air flow within the tubules,each of them is capped off at its lower end with a polyethylene plug 70having the form of a short cylinder with its upper end 71 cut at anangle of 30° its axis, as shown in FIG. 3. The lower end of that cutfaces a ⅝″-high {fraction (3/16)}″-wide slot 72, so that any drainingliquid can flow down the 30° slope and out through the slot. Tubule 68is made preferably of a thin thermoplastic material, such that itpermits forming a louver 74 by making one vertical and two parallelhorizontal cuts in the tubule so as to form three edges of a rectangleand pushing in the rectangular area so as to swivel it inward around thesecond vertical edge of the triangle, thus forming the structure shownin Section A—A′ of FIG. 3. This design imparts a swirling motion to theair flow within the tubule and assures that there are no obstructionsthat might cause clogging or retention of collected particles.

Operation at maximal sampling rates is desirable for two reasons. First,the amount of any collected air contaminants is proportional to thesampled volume and hence to the sampling rate. Secondly, the minimumparticle size that can be collected by a cyclone or a related device isinversely proportional to the square root of the sampling rate.Therefore, to increase the collection efficiency for 1-micron particles,the sampling rate should be as high as practicable for a given sampler.The main factor which limited the sampling rate in the older PHTLAASversions was excessive entrainment of liquid droplets by the outflowingair. This limitation was largely overcome by the modified fan-impellerconfiguration of FIG. 4, in which the outflowing airstream must goaround a co-rotating baffle before reaching the exhaust fan. As thebaffle co-rotates with the impeller, the larger droplets impinging uponit are spun off centrifugally onto the wall of the expansion chamber,whence they are collected into a liquid-retaining channel. Also spun offare particles which impinge on the co-rotating outer rim under the baseof the impeller. It is thus possible to increase the sampling rate to400 l/min, still without significant entrainment, with a rather lowpower input.

Another effect that was noticed at the higher flow rates was a gradualaccumulation of liquid in the upper expansion chamber and depletion ofliquid in the lower conical cavity. To prevent such accumulation anddepletion, the expansion chamber was modified to yield the liquidre-circulation and collection system of FIGS. 1 and 4, which alsoprovides a programmable interface to a sensor or a sensor array.

That system keeps removing liquid through line 21 from the retainingchannel 54 of FIG. 4 by gravity whenever line 21 is filled with liquid.The setting of the electrically programmable solenoid valve 17determines then whether the draining liquid is to feed a detector (orarray of detectors) through lines 23 and 29 or simply be re-circulatedinto the conical cavity through line 19.

To keep line 21 filled [i.e., bubble-free], liquid is continually fedfrom one of the reservoirs 13, 13′ by one of the electronicallycontrolled micro-purnps 15, 15′ and forced upward from the bottom ofline 21 so as to expel any trapped bubbles. The micro-pump is adjustedto supply the liquid at a rate that is sufficient to compensate fordepletion by evaporation, entrainment, and sample withdrawals to thedetector.

As shown in FIG. 4, the expansion chamber 7 is designed to minimizeentrainment of droplets and particles with the exhausted air stream andto permit recirculation and/or withdrawal of the contaminant-ennchedliquid solution or suspension that is generated by the interaction ofthe sampled air stream with the liquid carrier. The air stream 35leaving the sampling tube or tubes of the HTLAAS, such as one of thoseshown in FIG. 3, and entering chamber 7 through an opening 37, must goaround or impinge upon a baffle 39 before being drawn through windows 41into an exhaust fan impeller 43. Baffle 39 and windows 41 form part ofan integral cap-shaped piece 40, made preferably of a plastic materialsuch as polyethylene or polypropylene, which is affixed to the base ofimpeller 43, so as to co-rotate with it. Three wide substantiallyidentical and symmetrically disposed windows 41 are cut out of thecylindrical wall of the inverted cap 40 so as to leave baffle 39suspended on three equidistant legs 47 which form the vertical edges ofwindows 41. The rim 45 of cap 40 is affixed to impeller 43 on its flatupper side and has a rounded bevel 49 along the rim of its lower sidewhich permits smooth transfer of impinging particles and water dropletstowards the inner wall 53 of chamber 7 by the centrifugal action of therotating rim. The outermost edge 51 of cap 40 and the inner wall 53 ofchamber 7 form a fine clearance which is barely sufficient to permitfree rotation of the cap but too small to permit outflow of anysignificant part of the air stream.

The particles and droplets which are cast off the rim 45 onto thechamber wall 53 flow down that wall into a liquid-retaining channel 54and thence through a connecting tubule 55 into the recirculating line 21of FIG. 1.

Another improvement is the replacement of aqueous media by anon-volatile liquid, such as light mineral oil as the carrier fluid inthe PHTLAAS. If otherwise allowable, substitution of a non-volatileliquid for water greatly improves the performance of a PHTLAAS bypreventing dry-ups or freeze-ups under some weather conditions andextends its applicability to a wider range of ambient temperatures, fromas low as −30 C. to as high as 50 C. By cutting out evaporation losses,the use of mineral oil permits long-lasting operation over a widetemperature range without need to frequently replenish the liquid orprecondition the temperature and humidity of the air stream.

For instance, following injection of about 10 ml of mineral oil, theliquid film within the sampling tube exhibited a swirling flow patternover the entire inner surface, as pronounced as with water or perhapseven more so, which did not deteriorate after the sampler had beenoperated mostly unattended for over six hours at sampling rates of200-300 l/min.

The apparatus for substituting an alternative liquid carrier, such aslight mineral oil, corn oil, or dimethyl sulfoxide, for the water oraqueous solutions that are currently used in HTLAAS devices and forseparating any captured biological agents or other suspended matter fromthe lighter oil by gravity with the aid of sinking water droplets, isindicated in FIG. 5. Nonporous solid particles are usually heavier thanwater, and even living microorganisms, whose density is close to that ofa saline solution, i.e., ≧1.0 g/milliliter, would tend to settle out ofthe lighter oil [density ≦0.83 g/milliliter] if not prevented by mixing[convection] and surface action or colloidal effects. If the suspensionis confined within a vertical tubule 78 whose I.D. is not much largerthan the diameter of sinking water droplets 79. 79′, then the dropletswill act as nets, scooping up and sweeping down the suspended matteralong their way. This should accelerate the settling of suspended matterand of most hydrophilic solutes within a tiny water layer at the bottomof tubule 78 of FIG. 5.

A possible objection to the substitution of mineral oil or othernon-aqueous liquid for the heretofore used water or aqueous as theliquid carrier in HTLAAS devices is that non-aqueous liquids are notcompatible with most of the highly sensitive biological agent detectors,such as immunoassay-based sensors. Moreover, for maximum sensitivity, itis desirable that all or most of the captured particles be gathered intothe smallest practicable volume of the final liquid sample that is fedto detector 31. The concentrating device of FIG. 5 solves thecompatibility problem while minimizing the volume of the final liquidsample by efficiently transferring the captured particles from an oilcarrier to a tiny volume of water.

According to FIG. 5, an aqueous medium 76 is fed through line 27 to afine nozzle 80 whose orifice 82 faces downward, is coaxial with theinner wall 84 of tubule 78, and delivers droplets whose diameter is notmuch less than that of said inner wall. To prevent losses of droplets byaccidental contacts with and wetting of that wall, tubule 78 is made ofa hydrophobic material, such as Teflon or polyethylene. As the droplets79, 79′ sink down through tubule 78, they scoop up or sweep along anyencountered suspended particles and finally form or merge with a loweraqueous layer 86. When the level 88 of that layer reaches the level of avalve-controlled line 33, the flow of droplets is interrupted, Line 33is opened, and the oil is allowed to exit through it to an oil wastecontainer. Once the oil has drained out of tubule 78, Line 33 is closedand valve-controlled Line 29 is opened, so as to allow thecontaminants-enriched aqueous layer to drain into a detector 31. Oncethis drainage is completed, Line 29 is closed and tubule 78 can berefilled with a new contaminant-enriched oil suspension through the nowopened Line 23 until the oil level 90 reaches a predetermined heightrange.

For the device of FIG. 5 to work best, the diameter d_(d) of thedroplets must be carefully selected and matched with the internaldiameter [I.D.] of tubule 78, D_(t). For the droplet to sink easily,there must be enough room for the displaced oil to slip around it, whichimplies that the horizontal cross-sectional area of the droplet shouldnot be larger than half of that of the oil column. This imposes theinequality:

d _(d) ² ≦D _(t) ²/2  [3],

which also implies that a smoothly sinking droplet can not encounter andscoop up or sweep down more than 50% of the particles that are suspendedin the column. Therefore, for each droplet to be most effective, theInequality 3 should be close to an equality, i.e.,

d _(d) ≈D _(t)/2≈0.71D _(t)  [4].

Another important design consideration is the value of d_(d) Since thevolume is proportional to d_(d) ³, minimization of d_(d) with adherenceto Equation 4 should also minimize the final water volume. However, twoimportant factors will prevent us from pushing such minimization toofar. First, as droplet size decreases, surface effects become importantand slow down the sinking rate. Second, as d_(d) and D_(t) decrease, thecolumn height required to accommodate the 1- to 10-ml volume oil samplesfrom a PHTLAAS may become unmanageable. For instance, a 25-cm longcolumn would require a cross-sectional area of at least 0.04 cm²toaccommodate 10 ml of oil. This would require D_(t) to be at least 0.23cm and d_(d) to be about 0.16 cm [according to Eq 4], yielding a dropletvolume of around 0.003 ml, which is one tenth of the 0.03-ml dropletvolume that is usually coming out of a glass pipette. The smallervolumes can be generated by reducing the orifice size and substituting aless hydrophilic material for the glass. Thus, the basic approachreduces to optimizing d_(d) within the range 0.16 cm≦d_(d)≦0.3 cm, whileadhering to Equation 4, to implement the design of FIG. 5.

Therefore, to provide a collector-to-detector interface yielding aminimal sample volume, the components of FIG. 5 must satisfy thefollowing requirements for an optimal design. First, to generate waterdroplets of various known sizes within a selected range, e.g., of0.2-0.3 cm, the nozzle 80 must be made of such materials as glass,metals, Nylon, Teflon, polyethylene, polystyrene, etc. The droplet sizegenerated by a nozzle made of each of these materials can be deducedfrom the number of droplets required to yield a fixed volume of water.The rate at which a droplet of each size sinks through a column ofmineral oil or similar non-aqueous liquid can then be accurately timed.For instance, in one test, it took 24 seconds for a 0.05-ml droplet ofred wine to sink through an 8-cm column of white mineral oil.

For example, the best values of d_(d) and D_(t) and of the column heightH required to accommodate a 10-milliliter volume can be deduced from theformula

πD _(t) ² H/4≈10 cm³  [5].

Should Eq 5 yield a length H that is unmanageably long, then one canresort to a more complex concentrator having n parallel columns oflesser height h, such that nh=H. The shorter columns also offer theadvantage of shorter sinking times and hence faster separation ofsuspended particles from the oil.

The afore-disclosed apparatus can be used in various ways depending onthe hazards which are to be monitored or detected, as illustrated by thefollowing examples.

1. Detection of Concealed Explosives or Illicit Drugs

A successful system to detect explosives in buried mines and unexplodedordnance (UXO) must overcome the problem that the vapor concentrationsof some of the buried explosives are so low as to preclude theirreliable detection by even highly advanced vapor analyzers. Forinstance, cyclonite [RDX] and pentaerythritol tetranitrate [PETN] haveequilibrium vapor pressures of the order of a trillionth of anatmosphere. Although the equilibrium vapor pressures of otherexplosives, such as trinitrotoluene [TNT], are about 1000 times higherthan those of RDX or PETN, their actual vapor pressures near a buriedmine will be lower than the equilibrium pressure by several orders ofmagnitude because of depletion of vapor molecules by adsorption onto thesurrounding soil or dust particles and by being carried away byprevailing winds. The distribution profile of explosives molecules neara buried mine may therefore be expected to be mainly in the form ofadsorbates onto soil particles exhibiting a concentration maximum at thedepth of the mine and a minimum at the surface. Above the surface, anyexplosives molecules are likely to be present in the form of adsorbatesonto dust particles or onto wind-blown soil particles rather than invapor form. Moreover, the process of partial sublimation of a buriedexplosive and its adsorption onto the surrounding soil particles must berather slow, especially with explosives of very low vapor pressure.Therefore, the actual concentrations of explosives adsorbates will behighly dependent on the length of time since the explosive was firstburied. These concentrations may be expected to be substantially nilaround a freshly buried mine and reach nearly constant plateaus afterseveral months or years of burial. Therefore, to detect explosives thathave been buried for relatively short lengths of time [hours, days, or afew weeks] an extremely high sensitivity is required. This can beachieved with a system comprising [a] means for transferring subsurfacesoil particles into [b] an appropriate collector and thence to [c] anappropriate sensor or sensor array for ultra-low-level detection andidentification of any buried explosives.

Chemical detection of buried explosives is a particularly dauntingtechnical problem. Because of their low vapor pressures and thelimitations of detection technology, it is necessary to preconcentrateany captured traces of the analytes before introducing them into adetector. The above-discussed partial sublimation and adsorption ofexplosives molecules onto nearby soil particles may be viewed as anatural preconcentration process, which may be exploited for detectionpurposes by collecting some of these nearby particles and extractingadsorbates therefrom.

One way of collecting soil particles for such an analysis would be bymechanically scraping or digging into the surface and scooping up theloosened particles. However, such a mechanical action may cause enoughdisturbance to trigger an unwanted explosion. Gently swabbing the soilsurface may be effective in cases where the surface particles contain adetectible concentration of explosives adsorbates. However, due to theexpected steep concentration gradients emanating from a buriedexplosive, the probability of encountering detectible adsorbates will bevastly enhanced by probing deeper beneath the surface. A gentle,impact-free, and hence presumably safe method of such below-surfaceprobing would consist of blowing particles off the soil and collectingsome of the blown off particles into a high-volume air sampler, usingexhaust line 11 in conjunction with intake line 1 of FIG. 1.

As already noted, the detection of airborne chemical explosives in traceconcentrations presents a formidable challenge to existing sensingtechnologies primarily because of the extremely low concentrations ofexplosives that may be present in the vapor phase, especially in thecase of the relatively non-volatile “plastic” explosives, such as RDX orPETN. In view of the extremely low vapor concentrations, it seems almostmiraculous that dogs have been known to succeed where no present vaporanalyzer could even contend. The dogs' successes, widely attributed totheir ultra-sensitive olfactory system, may have been at least partlyhelped by the tendency of non-volatile vapors to preferentially adsorbonto particulates or be absorbed by water. Therefore, the surfaces ofsoil particles surrounding a buried mine may be partly covered byadsorbed explosives and, when these particles are blown into the air bya wind, they may carry with them a sufficient concentration of explosivematerial to be detected by a dog's highly sensitive nostrils followinginhalation, retention, and dissolution in the nostrils' liquid lining.If this interpretation of the dogs' successes has any merit, then asystem which captures particulates from a large volume of air andconcentrates them into a small volume of liquid extractant which is fedto an appropriate detector would most effectively mimic the dogs'prowesses.

Such a system is represented by the block diagram of FIG. 1. Forinstance, what is lacking in the sensitivity of any man-made detectorsas compared with that of the dog's nostrils may be at least partly madeup by the much faster throughput of a PHTLAAS—about 300 liters/min, ascompared with the dog's breathing rate of only a few liters/minute.Also, man-made instruments possibly approaching the sensitivity of adog's nostrils may be fluorescence-labeled or radioactivity-labeleddisplacement immunosensors, such as that reported by U. Narang, P. R.Gauger, A. W. Kusterbeck and F. S. Ligler, “Multianalyte detection usingcapillary-based flow immunosensor,” Anal Biochem, 255:13-19 (1998),which offer the advantages of high sensitivity and measurement speed forthe detection of low-vapor-pressure explosives of special interest, suchas TNT, RDX or PETN. A sensor of this type may be included in detector31 of FIG. 1.

Immunosensors can also serve for high-sensitivity detection of drugs andvarious other substances, whether chemical or biological, includingviruses and bacterial or fungal cells. Several low-vapor-pressureillicit drugs, such as cocaine or heroin, will similarly slowly adsorbonto surrounding dust particles, especially on dust settling near or onthe packaged drugs, and such particles when blown off by exhaust line 11may similarly reveal the presence of the drugs when picked up by intakeline 1.

Moreover, whereas a dog's nostrils can only pick up particles which areblown by a wind off the soil surface, the PHTLAAS of FIG. 1 can pick upthe more heavily explosives-covered particles from below the surfaceusing an attachment, such that the air exhaust and air intake lines fromand to the PHTLAAS terminate as two nearby parallel pipes, one of whichserves to blow soil particles out from beneath the surface, while theother line serves to draw some of the blown off particles into the airsampler for extraction of adsorbates and immunosensing. An adjustablefixture [not shown] for holding the two pipes in a fixed relationshippermits adjustments in the positioning and distance between the twopipes so that the amount of soil particles drawn in by the intake lineis large enough to yield a hefty signal but not so large as to causeclogging problems.

As estimated below, either the intake line opening should besufficiently far away from that of the exhaust line to keep the averageconcentration c_(s) of the sampled airborne soil particles below about0.007 g/L or else a programmed solenoid valve 3 may keep that openingblocked except for a short time interval during which only particlesoriginating from the deepest levels will be picked up in an amount notexceeding about 2 g.

To adapt present PHTLAAS instruments for collection and desorption ofsoil particles and for feeding an analyte-enriched liquid extractant toan immunosensor, it is necessary to provide [a] the liquid flow systemthat is indicated on the left side of FIG. 1; and [b] a waste outlet forthe processed particles, as indicated by line 33.

None of the previously disclosed work on the collection of airborneparticles by PHTLAAS devices dealt with dust-laden atmospheres. The highparticle concentrations generated by blowing the exhaust air into thesoil may cause clogging problems unless proper precautions are taken. Ifthe volume v_(e) of extractant in the PHTLAAS is to stay at least 10times larger than that of the soil particles, v_(o), then the totalweight of particles [of average gravity ρ_(s)≈2 g/cc] that are subjectedto extraction at any time must not exceed about 2 g for v_(e)≈10 ml. Ifthe residence time τ_(s) of a soil particle within the PHTLAAS is about1 min, then a steady state rate of uptake and removal of these particlesmust not exceed v_(o)ρ_(s)/τ_(s)≈2 g/min, which implies that for an airflow rate V_(A)≈300 L/min, the average concentration c_(s) of airbornesoil particles should not exceed

c _(s) =v _(o)τ_(s)/τ_(s) V _(A)≈0.007 g/L  [6].

Therefore, either the spacing between the air intake and air exhaustopenings must be set far enough for the intake to pick up the less denseportions of the generated dust or a solenoid valve must cause the intakeopening to be blocked most of the time, as suggested above.

To prevent an excessive build-up of particles within the PHTLAAS, theaverage rate of removal of processed soil particles should approximatelyequal the average rate of uptake, i.e., about 2g/min or 1 cc/min underthe above-postulated conditions. Such a rate of removal can be eithercontinuous, with a permanently open drain, or intermittent, i.e.controlled by a large-bore solenoid valve [not shown].

The waste from the processed soil particles can be either disposed of inthe field or stored in a container [not shown]. If the average rate ofremoval of processed particles is about 1 cc/min, then uninterruptedoperation over an eight-hour shift would require a waste container sizeof at least 0.5 L, and preferably 1 L to accommodate>8 hours ofoperation. Similarly, the liquid flowing through the detector at a rateof about 0.1 ml/min will require a container of about 50-100 ml todispose of the liquid waste over a similar length of time. The muchlarger volume of analyte-enriched extractant generated in the extractionprocess could be either discarded in the field or saved in properlymarked vials for follow-up analyses.

The air flow of about 300 L/min through the intake and exhaust lines canyield a wide range of air velocities by adjusting the cross sectionalarea of the exhaust opening. For instance, an area of 1 cm² yields anaverage air velocity of about 50 m/s, which is more than adequate toblow a sizable hole in most soils. A hole at least 1″ deep generatedwithin about 1 minute would yield about 25 g of blown off soil for anaverage concentration of about 0.1 g/L of particles suspended in an airstream of about 300 L/min. The position of the intake opening shouldthen be so adjusted that only about 10% of these particles get picked upby the PHTLAAS. Alternatively, the exhaust and intake openings may beadjacent to each other, but a two-way solenoid valve in the intake linecould be timed so as to allow the dusty air to be drawn for only thelast few seconds so as to pick up only the deeper soil particles.

To satisfy the requirements of rapid and efficient dissolution ofexplosives adsorbates from soil particles and of compatibility withsatisfactory operation of the PHTLAAS and of the immunosensor, it may benecessary to introduce two separate liquid extractants—acetone followedby the immunosensor's buffer solution. Acetone is known to be a veryefficient extractant for explosives in soil, but its high volatilitywould cause it to dry up rapidly in the hefty air stream of the PHTLAAS.However, by injecting an excess of acetone in the first minute of airsampling and following it up with an aqueous buffer solution while anadequate portion of the acetone still maintains full wetting of theparticles, we can effectuate a transfer of dissolved adsorbates from theacetone into the buffer solution, which will be followed by completeevaporation of the acetone from the buffer before its withdrawal intothe immunosensor.

The timing of the air flows through the PHTLAAS will have to be adjustedto conform with an optimal extraction treatment, preferably by anelectrically programmable control means. For the entire sampling andextraction process to be effectuated rapidly, the air flow may be set ata maximum rate, so as to draw the desired amount of soil particles intothe PHTLAAS in the shortest practicable time. The flow may then bereduced upon injection of the acetone to a rate that will suffice tokeep the mixture stirred up and swirling but without causing too rapidan evaporation of the acetone. The flow may then be increased uponinjection of the buffer solution to speed up the transfer of the analyteinto the buffer and the evaporation of the remaining acetone. Finally,the air flow may be stopped to permit withdrawal of the analyte-enrichedextractant and drainage of the treated soil particles. With each ofthese steps lasting a fraction of a minute, the entire cycle may becompleted within 2-3 min.

2. Monitoring for Pathogens in Food Processing Plants

In another embodiment of my invention, an alternative potential use forthe system of FIG. 1 is in the food processing industry. To monitor forharmful bacteria, molds, or viruses in processed foods, the exhaust line11 should have an adjustable orifice [not shown] which is provided witha HEPA [High Efficiency Particulate Arrestance] filter that will removecontaminants from the exhaust air. The orifice should be adjusted for asufficiently wide opening to yield only a moderate exhaust air velocitythat will barely suffice to blow off some droplets from liquids orloosely lodged particles or insects from solid or semi-solid foodswithout causing any significant splashing from the monitored areas. Someof the blown off droplets, particles or insects can then be drawn into aHTLAAS device 5 by the intake line 1 and collected in a film of mineraloil along the surfaces of the sampling tube 105 of FIG. 2 or of thesampling tubules 68 of FIG. 3. A suspension of the captured particles isthen carried over into the expansion chamber 7 [FIGS. 1, 2, and 4] andthence through the liquid-retaining channel 54 [FIG. 4] to line 21,valving 17, and line 23 into the concentrator 25, where the particlesare transferred into a tiny volume of aqueous solution that is ready fortesting in detector 25, in accordance with the above-explained scheme ofFIG. 5.

3. Monitoring for Insect-Borne Pathogens

A recent article by J. Morris, “When a pest turns menace,” U. S. News &World Report, Apr. 3, 2000, pp. 48-49, discusses the menace posed bymosquitoes in transmitting deadly pathogens, such as “dengue, malaria,yellow fever, and various forms of encephalitis, including West Nile.”Now, the suction at the air intake of a PHTLAAS is strong enough to drawin any nearby mosquitoes, and the trapped mosquitoes could be tested forthe above-cited pathogens.

The high air velocity at the air intake and the rapid swirling motion ofthe air within the PHTLAAS is strong enough to hurl any caughtmosquitoes against the inner wall of the sampling tube 105 or 68. If anon-aqueous liquid, such as mineral oil is used as the carrier, then anymosquito not killed by impacting the wall will be drowned or choked bythe oil film on that wall. If an aqueous solution is used as thecarrier, then inclusion of any insecticide, such as Malathion, willassure the death of any impacting mosquito. If the insecticide is a celllysing agent, such as tris[hydroxymethyl]aminomethane or the commercialproduct microLYSIS, supplied by Microzone Limited, Lewes, East Sussex,United Kingdom, then a sufficient quantity of DNA from a deadly virus orother pathogen may get dissolved or suspended in the carrier liquid tobe amenable to identification by PCR [Polymerase Chain Reaction] orimmunoassay techniques.

To increase the effectiveness of a PHTLAAS in capturing a sufficientnumber of mosquitoes for conclusive identification of pathogen threats,use can be made of known mosquito attractants, such as lighting, heat,and such chemical attractants as carbon dioxide from controlledsublimation of dry ice or controlled combustion of a flammable organicsubstance [propane, alcohol, or the like], lactic acid and/or1-octen-3-ol. The chemical attractants may be either fed into thecarrier liquid from one of the reservoirs 13, 13′ . . . and transferredat a controlled rate into the sampled air stream or else they can beinjected through a separate line [not shown] into the exhaust air thatis emanating from the PHTLAAS. To distribute such attractants over awide area, the exhaust air should be emitted from a large openingthrough a wide angle.

The following potential advantages are seen in using HTLAAS devicesrather than other known mosquito traps. First, the suction at the airintake and the high air sampling rate of some 300 L/min or faster assurethat a much larger number of approaching mosquitoes will be capturedthan with passive insect traps. Furthermore, the concentration ofchemical attractants in the exhausted air can be controlled far betterthan with other devices using the system of FIG. 1, and thatconcentration can be optimized to attract mosquitoes and otherblood-sucking insects from a much wider area. Moreover, the compositionof the carrier liquid can be controlled so as to not only assure instantdeath or incapacitation of any impacting insects but also to facilitatelysis of the insects' cells and transfer of the suspended insects, theirlysed cells, and their released DNA components for appropriate testingand pathogen identification procedures.

4. Monitoring for Lead, Hexavalent Chromium, and Other Hazardous Metalsand Their Compounds

Besides monitoring for solely airborne hazards, a HTLAAS instrument canbe provided with a dual-line air exhaust and air intake adapter and usedto detect lead, hexavalent chromium, and other hazardous metals andtheir compounds in crumbling walls or paint, in soils, especially sand,and in other contaminated areas. The ability of the PHTLAAS to collectboth vapors and aerosols from the sampled air should be especiallyuseful in applications where a significant fraction of the airborneanalyte may be in form of vapor (e.g., organometallic compounds, such asmethyl mercury or tetraethyl lead), solid particles or liquid droplets.

The extractant that is to be used in preferred embodiments of theinvention will depend on the analyte of interest. To dissolve leadcompounds, such as lead oxide (PbO), lead carbonate (PbCO₃), or leadnitrate (Pb(NO₃)₂), a solution of acetic acid or acetate may suffice, asdisclosed in detail in my afore-cited co-pending applications Ser. Nos.08/377,966 and 08/851,428. To solubilize metallic lead, an oxidant needsto be added to the extractant. The effect of pH and of acetic acid,acetate, and oxidant concentrations in water on the rate ofsolubilization of metallic lead at 20° C. is shown in FIGS. 4-6 of theco-pending application Ser. No. 08/377,966. At a pH of 5 or less, aslittle as 0.1 M of sodium acetate or acetic acid plus 1 weight-% H₂O₂suffices to yield an etching rate of about 10 microns/min, which impliesthat particulates in the respirable size range of <5 microns willcompletely dissolve in such a solution within a fraction of a minute.

Indeed, when 1-mL portions of an extractant containing 0.3 M acetic acidplus 3% hydrogen peroxide were added to 1-mg samples of powdered leadcarbonate (passed through a 325×325 mesh gauze that retained particlesof sizes >40 microns), lead oxide, or lead nitrate, complete dissolutionof the powders occurred within less than a minute. It therefore appearsthat a solution containing 0.1-1 M of acetic acid or acetate ions plus1-10% of hydrogen peroxide is adequate for the solubilization oflead-containing particulates, provided that its acidity is kept at a pHof 5 or less. Furthermore, for use with the PHTLAAS, the preferredconcentration range is 0.1-0.3 M of acetic acid plus acetate ions and1-3% of hydrogen peroxide.

The analytical means that is to be used will again depend on the analyteof interest. For the detection of lead in aqueous solutions under fieldconditions, a calorimetric or electroanalytical method appears to bemore cost effective than an alternative method based on atomicabsorption spectroscopy (NIOSH Method 7082), especially for use underfield conditions, as detailed in my above-cited co-pending applications.

Similarly, to screen for Cr⁺⁶ compounds, the concentration ofcarcinogenic Cr⁺⁶ can be measured by a technique which uses an aqueousalkaline solution, as described in publications by S. A. Katz, “TheAnalytical Biochemistry of Chromium,” Environ. Health Perspect.,92:13-16 (1991), and D. C. Greene, S. Pepe, F. Dolinsek, and S. A. Katz,“Determination of Hexavalent Chromium in Some Contaminated Soils fromHudson County, N.J.,” J. Environ. Sci. Health, A27(3):577-586 (1992).Samples collected by the PHTLAAS should be readily analyzable by thistechnique. Portable kits for the determination of Cr⁺⁶ in water aremarketed by the Hach Co. [Loveland, CO 80539]. Their listed “smallestincrement” of 0.05-0.1 mg/l translates to a detection limit for Cr⁺⁶ ofabout 0.01 mg/m³ of air using a PHTLAAS that samples air at a rate of200-300 l/min for 3-5 minutes and collects the contaminants into aliquid volume of about 10 ml at an efficiency of 20-30%.

If it is desired to monitor solely the content of respirableparticulates, a flow-deflecting largeparticle impactor, such as thatshown in FIG. 2, may be interposed at the air intake so as to collectthe larger particles outside the PHTLAAS, while allowing the smallerparticles to flow unhindered through the intake with the sampled air.

5. Testing Soils, Homes, Work Areas, and Ambient Air for PotentialCarcinogens

In attempts to reduce people's exposure to cancer-inducing soil and aircontaminants, the conventional, rather laborious and expensive procedureis to test soils and air for the presence of specific known or potentialcarcinogens frequently using costly instrumentation and analyticalmethods that were developed and preferably approved by the EnvironmentalProtection Agency for each specific substance. This approach may beappropriate in cases where only a few carcinogens are expected to pose apotential hazard to be monitored. For instance, in many industries,laboratories, offices, and even homes, formaldehyde may pose a fairlywidespread cancer hazard which can be detected with PHTLAAS instruments[see C. S. Woo, S. E. Barry, and S. Zaromb, “Detection and Estimation ofPart-per-Billion Levels of Formaldehyde Using a Portable High-ThroughputLiquid Absorption Air Sampler.” Environ. Sci. Technol. 32:169-176(1998)]. In decommissioned or malfunctioning nuclear reactors, tritiatedwater may pose a radio-activity threat which may be monitored asdescribed in a paper by S. Zaromb, A. Justus, W. Munyon, D. Reilly, andB. Chen, “A Novel Portable Grab Sampler for Tritiated Water Vapor.”Health Phys. 72(3):480-484 (1997)]. However, this approach has turns outto be costly and ineffective where more than a few potential carcinogensmay be present or where the hazard is posed by an unknown carcinogen.For instance, the cause of a mysterious incidence of brain tumors amongemployees of an Amoco laboratory in Illinois has never been discovered,in spite of all the elaborate and expensive tests that were conducted infutile attempts to pinpoint it.

A far more effective and far less expensive alert to a probable presenceof carcinogens in ambient air, or in contaminated soils, homes or workareas, is based on a combination of a HTLAAS technology with any one ofthe established tests for mutagenicity of aqueous samples, such as thewell known, relatively inexpensive but slow Ames test or the more costlybut faster Mutatox tests, as discussed below. These tests have so farbeen used solely for water-containing samples. By subjecting thepollutant-enriched water samples that are collected by a HTLAAS toeither of these mutagenicity tests, we provide an effective andrelatively inexpensive alert for soil-impregnated or airbornecarcinogens and other mutagens. Also, with a dual-line intake-exhaustadapter, as per the scheme of FIG. 1, it is also possible to use thesame approach to contaminant-impregnated soils, work areas, or evenhomes.

Relatively inexpensive “Mutagen Detection Ames Modules” are availablefrom Microbix Education Systems, Toronto, Canada. Although an Ames testtakes several days to complete, each module permits simultaneou testingof many samples for carcinogens and other mutagens, so that the averagetime per test is effectively short.

Much faster but much more expensive testing can be performed with aMicrotox/Mutatox System, supplied by AZUR Environmental, Carlsbad,Calif., which can test aqueous samples for acute toxicity, chronictoxicity, and mutagenicity. Contaminant-enriched water samples from aHTLAAS device could be tested not only for mutagenicity but also foracute or chronic toxicity using a technology that is based on therespiratory physiology of Vibrio fischeri (formerly, Photobacteriumphosphoreum), a naturally luminescent marine bacterium. When properlymaintained and grown, certain strains of luminescent bacteria divertabout ten percent of their metabolic energy into a special metabolicpathway that converts chemical energy, through the electron transportsystem, into visible light. This pathway is intrinsically linked to therespiration of the cell [A. A. Bulich, 1979. “Use of luminescentbacteria for determining toxicity in aquatic environments.” In: AquaticToxicology, ASTM STP 667, L. L. Marking and R. A. Kimerle, Eds.,American Society for Testing and Materials, pp. 98-106].

The test for acute toxicity measures a decrease in light output. Achange in cellular metabolism or a disruption of the cellular structureresults in a change in respiration and a concomitant change inbioluminescence. This physiological endpoint is used to monitor the“health” of the cells before and after a fifteen-minute exposure [P. E.Ross, 1993. “The Use of Bacterial Luminescence Systems in AquaticToxicity Testing.” Chapter 13 in: M. Richardson (ed.) EcotoxicologyMonitoring. VCH Publishers, New York]. Toxicity is estimated as afunction of inhibition of luminescence, relative to controls, in aconcentration-response relationship. The test for chronic toxicity usesthe same measurement (inhibition of luminescence) but at a sensitivitythat is heightened with a longer exposure time, so that lowerconcentrations of toxicants can be detected [see the above-cited Ross,1993].

The test for genotoxicity, or mutagenicity, uses a mutant strain of V.fischeri in which the luminescence capability is repressed [S. Ulitzur,I. Weiser and S. Yannai. 1980. “A new sensitive and simplebioluminescence test for mutagenic compounds.” Mut. Res. 74: 133-124].When this dark mutant strain is exposed to genotoxic chemicals, some ofthe cells will undergo the reverse mutation, becoming luminescent [K. K.Kwan, B. J. Dutka, S. S. Rao and D. Liu. 1990. “Mutatox test: a new testfor monitoring environmental genotoxic agents.” Environmental Pollution.65: 323-332]. Three types of mutagens have been detected with theMutatox test: direct mutagens (base-substitution or frame-shift agents);DNA damaging agents or DNA synthesis inhibitors; and, DNA-intercalatingagents [S. Ulitzur, 1986. “Bioluminescence test for genotoxic agents.”Methods in Enzymology. 133: 264-274]. Genotoxic potential is estimatedas a function of increase in luminescence, relative to controls.

The Mutatox assay for genotoxic agents uses the dark mutant strain of V.fischeri in which a forward mutation has disabled the luminescencecapability of the cell. The test system is comprised of freeze-driedluminescent bacteria of the dark mutant strain, a temperature-controlledphotometer, and a data capture and analysis protocol supplied via adesk-top computer. Standardization is maintained by supplying cells in afreeze-dried form designed to capture and maintain their optimumphysiological state. This method of preservation assures consistentsensitivity and specificity of the test. A range of sampleconcentrations is tested, and a luminescence response greater than threetimes the control luminescence is considered to be a genotoxic event.

There will now be obvious many variations and modifications of theafore-disclosed embodiments to persons skilled in the art. It will beobvious that similar approaches can apply to the detection andmonitoring of illicit drugs and many hazardous substances, e.g.,comprising cadmium, zinc, chromium, uranium, or compounds of thesemetals, miscellaneous carcinogens, and other toxic contaminants, thatcan be either absorbed directly in a suitable liquid extractant orsolubilized therein from collected airborne particulates. All of thesevariations and modifications will remain within the scope of thisinvention if defined by the following claims.

What is claimed is:
 1. A method of detecting the presence of a harmfulchemical or biological substance or trace thereof comprising the stepsof: pumping air through a container having an air inlet opening and anair exhaust opening; collecting said substance or trace from said volumeof air into a small volume of a liquid carrier within said container;and transferring said carrier into an appropriate means for detection ofsaid substance or trace, which comprises extracting said substance ortrace from collected insects or other particulates into a carrier liquidso as to form an analyte-enriched liquid sample.
 2. The method of claim1, wherein said liquid carrier comprises acetate ions for dissolvinglead-containing analytes or an aqueous alkaline solution for dissolvinghexavalent chromium.
 3. The method of claim 1, wherein at least part ofthe analyte is in the form of a metal and said carrier liquid comprisesan oxidant that is able to oxidize said metal.
 4. The method of claim 1which comprises detecting the presence of mutagens in air, soils, homesor work areas by testing said carrier liquid for mutagenicity.
 5. Themethod of claim 1 which comprises drawing air from selected spaces whichmay contain said substance into said inlet opening through an air intakeline.
 6. The method of claim 5 which comprises adding to said pumped airan insect attractant at a controlled rate and emitting said air throughsaid exhaust opening over a wide angle so as to attract pathogen-bearinginsects toward said air intake line.
 7. The method of claim 6, whereinsaid insects are mosquitoes and said attractant comprises carbondioxide, lactic acid, and/or octenol.
 8. The method of claim 5 whichcomprises directing air from said exhaust opening through an exhaustline and outlet aperture onto selected surfaces which may contain saidsubstance, so as to blow off insects, solid particles or liquid dropletstherefrom, and positioning said intake line so that many of the blownoff insects, particles or droplets are drawn through said intake lineinto said container.
 9. The method of claim 8, wherein said outletaperture is adjusted so as to yield a focused air stream which iscapable of blowing a hole of a diameter that is comparable to that ofsaid aperture in various types of earth other than hard rock so as tocause deeper soil particles to be picked up by said intake line andthereby facilitate detection of buried explosives or other soilcontaminants.
 10. The method of claim 8, wherein said substance is apathogen or other contaminant in food.
 11. A method of detecting thepresence of a mutagenic substance or trace thereof in air whichcomprises the steps of: pumping air through a container having an airinlet opening and an air exhaust opening; collecting said substance ortrace from said volume of air into a small volume of a liquid carrierwithin said container wherein said collecting comprises extracting saidsubstance or trace from said air to said liquid carrier so as to form asubstance-enriched or trace-enriched liquid sample; and transferringsaid carrier into an appropriate means for testing said liquid formutagenicity.
 12. The method of claim 11, wherein said testing follows aprocedure from the Ames test or a variation thereof.
 13. The method ofclaim 11, wherein said testing comprises measuring the luminescence of amutant strain of Vibrio fischeri.